Abstract:
Investigations of Lower Pennsylvanian coal-bearing rocks for the central Appalachian basin analysis program have delineated a broad sinuous channel extending for 30 mi northwestward from Richlands, Virginia.
Named herein the Richlands channel, the bed of this fluvial channel is as much as 6 mi wide and truncates as much as 125 ft of the underlying strata along a regionally significant disconformity. The channel is at the base of the Dismal sandstone member of the New River Formation and is filled with polymictic conglomerate and conglomeratic subgraywacke consisting mainly of well-rounded quartz pebbles that decrease in size toward the northwest. The northwest end of the channel is at a strandline marked by a well-winnowed orthoquartzite of a northeast-trending, barrier-bar complex. The absence of the characteristic deltaic morphologies, which are typical of fluvial sandstones in the underlying Pocahontas Formation, suggests that sediments at the channel terminus may have been reworked and redeposited by the southeastward-transgressing Appalachian seaway. The Richlands channel and other channels in the New River and Pocahontas Formations in the Richlands area define a major depocenter for Early Pennsylvanian clastics that were prograding from the southeast—a relationship that fits the barrier model applied to these strata rather than a braided, southwestward-flowing river system.
